Complex-Regge-Pole Model Consistent with the Dual Absorption Picture: Meson-Baryon Charge-Exchange Reactions

The reactions π^-p→π⁰n, π^-p→ηn, K^-p→K̄⁰n, and K⁺n→K⁰p, where ρ and/or A₂ exchanges are involved, are considered within the complex-pole model with the amplitudes given by γ₊ξ₊s^α₊+γ_-ξ_-s^α_-. Our fits confirm the prediction of the dual absorption model in that we find the real part of the residue function, γR, to be ~Jₙ with $n=0, 1$. For the imaginary part, γI, we find that since the j-plane cuts are strong for the spin-nonflip amplitude we have γI~-H₀, the Struve function, whereas the cuts are weak for the spin-flip amplitude so that γI~0. The contribution of γI to the amplitude always appears in the form αIγI, which is quite small. Good quantitative fits to all the data are obtained in terms of only four parameters for the exchange-degenerate ρ, A₂ residue if we take J₀(R₀(-t)1/2)∓iH₀(R₀^'(-t)1/2) as the nonflip residue and J₁(R₁(-t)1/2)R₁(-t)1/2∓iλαI as the flip residue with R₀≈R₀^'≈R₁≈1 F and λ<1. For the imaginary part of the trajectory function we find 〈αI〉_ρ=0.17 and 〈αI〉A=0.26. The presence of nonzero αI removes the need for any explicit ghost-eliminating factors. A detailed discussion of this model as well as a comparison with other models is made.